Air raid warning system



March 12, 1946. I c HlNEs I 2,396,422

' AIR RAID WARNING SYSTEM Filed April 30; 1942 2 Sheets-Sheet l INVENTOR glaudeMHi-nes M 9 ATTORNEY Patented Mar. 12, 1946 AIR RAID WARNING SYSTEM Claude M. Hines, Pittsburgh, Pa., assignor to The Westinghouse Air Brake Company,wilmerding, Pa., a corporation of Pennsylvania Application April .30, 1942, Serial No. 441,197

'7 Claims.

This invention-relates to air raid warning systems and has particular relation to automatic control equipment for selectively producing any one of a plurality of different coded signals, indicative of air raid. all clear, and the like,

In the copending joint application of Robert A. Mitchell and the present applicant Claude M. Hines, now Patent 2,381,224, issued August '7, 1945, there are disclosed air raid warning systems for automatically and selectivel controlling the operation of warning devices, such as air operated or electrically operated horns, to produce different coded signals indicative of air raid and all clear. The apparatus in this copending application includes a signal coding and timing device which is operated by an air engine.

It is an object of my present invention to provide an air raid warning system of the type disclosed in the above-mentioned ccpending application and characterized by signal coding and timing apparatus not requiring an air engine for operation.

More specifically, it is an object of my present invention to provide an air raid warning system of the type indicated in the foregoing object and including signal coding and timing apparatus differing specifically from that in the aforementioned Patent 2,381,224.

The above objects and other objects of my invention which will be made apparent hereinafter are attained by apparatus subsequently to be described, and shown in the accompanying drawings, wherein:

Fig. 1 is a diagrammatic view showing an air raid warning system embodying my invention,

Fig. 2 is a development view of the commutator which is a part of the signal coding apparatus disclosed in Fig. 1,

Fig. 3 is an end view of the coding and timing apparatus shown in Fig. 1, showing further details of construction,

Fig. 4 is a iragmental enlarged sectional view taken on the line 4-4 of Fig. 3, showing a further detail of construction,

Fig, 5 is a fragmental diagrammatic view showing a modification of the system of Fig. l, in which an electrically operated signal device is employed rather than an air operated signal device,

Fig. 6 is a diagrammatic view showing another embodiment of my invention and including a different type of signal coding and timing apparatus from that shown in Fig. l, and

Fig. '7 is a diagrammatic view showing a modification of the embodiment shown in Fig. 6.

Description of system shown in Fig. 1

The system shown in Fig. 1 comprises an andible signal device in the form of an air operated horn l I; a source of air under pressure such as a reservoir 12 which is charged to a certain operating pressure such as one-hundred pounds per square inch, by a suitable air compressor not shown; a magnet valve device l3 for controlling the supply of air from the reservoir l2 to the horn H a signal coding and timing device M for controlling the operation of the magnet valve device l3; an electric motor 15 for operating the signal coding and timing device l4; and additional control apparatus including two remotely controlled relays l5 and I7, two additional relays l8 and I9, respectively, controlled by the relays l6 and I1, two push button switches 2| and 22, and two additional switches 20a and 20b. The equipment further includes a suitable source of direct-current such as a storage. battery 23, the positive and negative terminals of which are respectively connected to two bus wires 24 and 25, hereinafter respectively referred to as the positive bus wire and the negative bu wire.

Considering the parts of the equipment in greater detail, the air operated horn I I may be of the type shown in Patent 2,263,342 to Norman 'F. Lewis, in which the vibration of a sound-producing diaphragm is efiected in response to the continuous supply of air under pressure to the horn.

The particular construction of the horn H is, however, not material to my invention inasmuch as any horn device operated in response to the supply of air under pressure thereto may be employed.

The magnet valve device l3 may be any standard type. As diagrammatically shown, it may comprise a suitable casing having a chamber 21 to which the reservoir I2 is constantly connected by a pipe 28, a chamber 29 to which the horn H is constantly connected the pipe 3|, a valve 32 of the poppet type controlling communication between the chambers 21 and 29, and a magnet winding 33 for operating the valve 32.

The valve .32 is normally urged upwardly to a seated position, closing communication between the chambers 28 and 29, by a coil spring 34 and unseated downwardly in response to energization of the magnet winding 33 by means of :a suitable plunger 3.5 actuated by the magnet winding.

It will thus be seen that when the magnet winding 33 is deenergized, the supply of air to the horn H is out off and the horn is silent. It will also be seen that whenever and as long as the magnet winding 33 is energized, air under pressure is supplied to the horn l to cause it to produce an audible signal or blast.

It is preferable to employ a horn which is not directionally selective. Obviously, if directionally selective horns are employed, then a plurality of horns each pointed in a different direction may be connected, in multiple, to the pipe 3!.

The signal coding and timing device l4 comprises a rotary shaft 31 suitably mounted for rotation in a supporting casing, not shown, and adapted to be rotated at a suitable speed by the motor l5 through a speed reduction gear mechanism 38. The shaft 31 is eifective upon rotation to cause operation of a coding switch formed by a commutator 39 fixed on the shaft and two stationarily supported insulated brushes 4| and 42 associated therewith. The commutator 39 may comprise a suitable disk of insulating material carrying on the outer periphery thereof a continuous contact ring 43 from which a desired number of contact fingers 44 projects axially in regular spaced relation circumferentially (see Fig. 2). The surfaces of the contact ring 43 and contact fingers 44 are fiush with the portion of the insulating disk between the respective contact fingers, thereby forming a smooth contact face for the commutator.

The brushes 4| and 42 are supported in insulated relation by a suitable brush holder in such a manner that the brush 4| continuously engages the contact ring 43 and the brush 42 engages the contact fingers 44 successively upon rotation of the commutator 39.

Brushes 4| and 42 are thus periodically connected and disconnected for substantially equal intervals of time, respectively, upon rotation of the commutator 39 at a constant speed.

The motor [5 is indicated as of the direct-current shunt field type and rotates at substantially constant speed. in response to a predetermined voltage impressed thereon, thereby causing rotation of the shaft 3! at a predetermined selected speed. The speed of rotation of shaft 3'! is such that the commutator 39 completes one full revolution in a certain length of time, such as two minutes.

The brushes 4| and 42 are thus connected and disconnected alternately for predetermined and substantially equal intervals of time, the length of which depends upon the number of contact fingers 44 and the corresponding number of insulating segments between the commutator fingers 44. Thus, as shown in Fig. 2, the commutator 39 has ixteen contact fingers 34 and a corresponding number of insulating segments between the contact fingers. Assuming a complete revolution of the shaft 31 and commutator 39 in two minutes, it will be seen that the brushes 4| and 42 are connected and disconnected alternately for approximately three and three-quarters seconds.

It will be apparent that the width of the contact fingers 44 with respect to the insulating segments between the contact fingers may be varied so that the length of time that the brushes 4| and 42 are connected with respect to the length of time that they are dis-connected may correspondingly vary.

The coding and timing device i4 further comprises a timing switch device including a rotary cam disk 46 fixed on the shaft 31 and rotatable therewith and two switches 41 and 48 of the telephone type associated therewith and operated thereby.

Each of the switches 47 and 48 comprises a pair of contact fingers having contacts which are normally biased into contact with each other, the contact fingers of the two switches being carried in insulated relation by a suitable support 5|. One of the contact fingers of the switch 41 and a corresponding one of the contact fingers 43 are extended and provided with a suitable insulating button 52 on the end thereof which slidably engages a corresponding face of the cam disk 46.

At one point adjacent the periphery of the cam disk 43 are two cams 53 which are in axial alignment on opposite faces of the cam disk, as shown in Fig. 4. The cams 53 may be formed in a convenient manner by a single element in the form of a rivet extending through a suitable hole in the cam disk 49 and having the opposite ends suitably rounded to form the cams 53.

The cams 53 are located the same radial distance from the axis of rotation of the shaft 31 as are the insulating buttons 52 on the contact fingers of the switches 41 and 48. It will thus be seen that as the cam disk 46 rotates through one certain position, the cams 53 engage the insulating buttons 52 to bend the corresponding contact fingers of the switches 41 and 49 outwardly from the corresponding faces of the cam disk to cause separation of the contacts carried by the contact fingers. After the cam disk 43 has passed through such certain position, the contact of the two switches 41 and 48 reengage.

The cam disk 46 is fixed on the shaft 3'! in such a manner as to cause opening of the switches 41 and 48 at a certain selected time in the manner hereinafter to be more fully explained.

The commutator 39 of the signal coding device l4 differs somewhat from that disclosed in the above mentioned Patent 2,381,224 of Robert A. Mitchell and Claude M. Hines for the reason that in'the present application the commutator 39 rotates continuously whereas, in the patent, the commutator is alternately moved and stopped while being progressively shifted rotatively.

The relays I6 and I! are standard direct-current relays of the neutral type, each having a winding W and a single front contact a. The windings W of the relays l6 and I1 are connected by suitable wires to a remote control station where they may be selectively energized and deenergized by an operator. Such remote control station may be a telephone exchange where an operator is always on duty.

The relays l8 and I9 are standard direct-current relays of the neutral type. Relay i8 has a winding W, two front contacts a and b, and a transfer contact 0. Relay J!) has a winding W and three front contacts a, b, and 0, respectively.

It will be understood that the term front contact" refers to a contact which is in open position when dropped-out and in closed position when picked-up while the term transfer contact refers to a contact which is in one closed position when dropped-out and a different closed position when picked-up.

The push button switches 2| and 22 may be of any standard type requiring the application of manual pressure to close them and to main tain them closed, and being automatically opened upon the release of manual pressure.

The switches 20a and 20b may be of any singlepole, single-throw type, such as a knife switch or a snap switch of the rotary type. These switches will be hereinafter referred to as cutout switches because they are effective, when opened, to cut the relays l6 and I! out of operation in'the manner hereinafter to he pointed out.

Operation of system shown in Fig. 1

Let it be assumed that the operator at the remote control station desires to cause the horn I I to signal an air raid. To do so, he operates a switch (not shown) at the remote control station, thereby causing energization of the magnet winding W of the relay I6 for a short interval of time.

The contact a of the relay I6 is accordingly actuated to its picked-up or closed position and is effective in such position to establish a circuit for energizing the winding W of the relay I8. This circuit extends from the positive bus wire 24' by way of a branch wire 51, another branch wire 58, contact a of the relay I5, and a Wire 59, including in series relation therein the cut-out switch 29a and the winding W of the relay I8, to the negative bus wire 25.

The contacts of the relay I8 are accordingly actuated to their picked-up position. The contact b of the relay I8 is effective in its picked-up or closed position to establish a self-holding circuit for the winding of the relay l8. This circuit extends from the positive bus wire 24 by way of the branch wire 51, a wire 6| including in series relation therein the contact 2) of the relay I8 and the switch 41 of the signal coding and timing device I4 to the wire 59, and thence through the winding W of the relay I8 to the negative bus wire 25.

It will thus be seen that once the relay I8 is picked-up it holds itself picked-up thereafter, thereby permitting the contact of the relay It to be restored to its dropped-out position. In other words momentary pick-up of the relay I5 causes the relay I8 to be picked-up and maintained picked-up thereafter until the happening of an event subsequently to be described.

The contact a of the relay I8 is efiective in its picked-up or closed position to establish a circuit for energizing the motor I5. This circuit extends from the positive bus wire 24 by way of the branch wire 51, a wire 62 including in series relation therein the contact a of the relay l8 and the parallel-connected armature and field windings of motor I5, to the negative bus wire 25.

The motor I5 is accordingly rotated to cause rotation of the shaft 31 of the signal coding and timing device at a substantially constant speed.

The contact 0 of the relay I8 is effective in its picked-up position to establish a circuit for energizing the magnet winding 33 of the magnet valve device I3. This circuit extends from the positive bus wire 24 by way of the Wire 51, contact 0 of the relay I8 in its picked-up position, a wire 54 including in series relation therein the signal coding switch, formed by the brushes M and 42 and the commutator 39, and the magnet winding 33 of the magnet valve device I3, tothe negative bus wire 25.

It will thus be seen that the magnet valve device I3 is periodically operated to cause air under pressure to be supplied from the reservoir I 2 to the horn I I as the commutator 39 of the signal coding and timing device I4 continues to rotate. The horn II accordingly is operated to emit an audible blast or signal periodically for a length of time corresponding to the length of time that the brushes 4! and 42 are connected by the commutator 39. As previously explained, the brushes 4| and 42 are alternately connected and disconnected for substantially equal lengths of time of approximately three and three-quarter seconds. Thus the audible signals produced by the horn II are separated by silent intervals of substantially the same duration.

The horn II continues to operate to produce the coded signal, indicative of an air raid, in the manner just described as long as the relay I8 remains picked-up. The relay i8 is restored to its dropped-out position due to the interruption of the self-holding circuit thereof in response to the opening of the switch 41 of the signal coding and timing device I4. The cam disk 46 is normally so positioned with respect to the switches 47 and 48 that the shaft 31 rotates through substantially a full revolution before the cams 53 on the cam disk 46 engage the insulating buttons 52 on the contact fingers of the switches 41 and 49 to cause opening of the switches. Accordingly, it will be seen that the relay [8 is not restored to its dropped-out position until the shaft 31 completes substantially one full revolution following the initial pick-up of the relay It, thus automatically timing the duration of the signal sequence.

Upon restoration of the contact a of the relay I8 to its dropped-out or open position, the circuit previously traced for energizing the armature and field windings of the motor I5 is interrupted. Due to the inertia of the motor armature and the other rotating parts rotated thereby the motor armature rotates sufficiently long, after interruption of the energizing circuit in response to the restoration of the relay I8 to its dropped-out position, to insure the cams 53 on the cam disk 45 passing the switches 41 and 48 so as to reclose the switches before the shaft 31 is stopped. Obviously, once the contact b of the relay I8 is restored to its droppedout or open position, the reclosure of the switch M is ineffective to restore the self-holding circuit for the winding of the relay I8 and consequently the relay It remains in its dropped-out position thereafter unless again picked-up in the manner previously described by operation of the relay I6 or by means of the push button switch M in the manner presently described.

If the local operator desires to cause operation of the horn I I to produce the coded signal indicative of an air raid he ma do so merely by momentarily closing the push button switch 2|. The switch 2I is connected in parallel with the contact a of the remotely controlled relay I6 and accordingly is effective upon closure to cause pick-up of the relay I8 in the same manner as if the relay I5 is picked-up.

The operation of the equipment to produce a periodic blast of the horn I l for a predetermined time is thus effected in the same manner as previously described and the description accordingly is not repeated.

If the local operator for any reason desires to cut the remotely controlled relay I 6 out of operation he may do so merely by opening the cutout switch 20a. The switch 29a, being in series with the contact a of the relay I6 and the winding of the relay I8, is effective when opened to render the pick-up of the relay IE ineffective to cause pick-up of the relay I8.

Now let it be supposed that the operator at the remote control station desires to cause operation of the horn II to produce the all clear signal. To do so, he closes a switch for causing energization of the winding W of the relay H, the contact a of which is accordingly actuated to its pickedup or closed position. The contact a of the relay !'I is eiTective in its pick-up position to cause energization of the Winding W of the relay I9. This circuit extends from the positive bus wire 24 by way of the wires 51 and 58, contact a of the relay I7, and a wire 65 including in series relation therein the cut-out switch 20b and the winding W of the relay I9 to the negative bus wire 25, The contacts of the relay I9 are accordingly actuated to their respective pick-up or closed positions.

The contact b of the relay I9 is effective in its picked-up or closed position to establish a selfholding circuit .for the winding W of the relay I9, thus permitting restoration of the contact of the relay il to its dropped-out position once the relay It is picked-up. This self-holding circuit for the winding of the relay I9 extends from the positive bus wire 24 by way of the wire 51, contact c of relay E8 in its dropped-out or closed position, and a wire 69 including in series relation therein contact b of the relay I9 and switch 48 of the signal coding and timing device I4 to the wire 85, and thence through the winding W of the relay is to the negative bus wire 25.

The contact a of the relay I9 is connected in parallel with contact a of the relay I8 and is therefore effective, in its picked-up position, to cause energization of the armature winding and field winding of the motor I in the same manner as does the contact a of the relay I8. Accordingly, the motor I5 starts to rot-ate the shaft 31 the instant the relay I9 is picked-up and continues to rotate it until such time as the relay I9 is restored to its dropped-out position in the manner presently to be described.

The contact I) of the relay I9 is efi'ective in its picked-up position to cause energization of the winding 33 of the magnet valve device I3 independently of the coding switch including the brushes iI and i2 and commutator 39 of the coding and timing device I 4. This circuit extends from the positive bus wire 24 by way of the wire 5?, a wire ii having in series relation therein contact I) of the relay I9 to the wire 64 at a point 12 between the brush 42 and the winding 33 of r the magnet valve device I3, thence by way of the wire 5- and winding 33 of the magnet valve device I3 to the negative bus wire 25.

It will thus be seen that although the shaft 31 continues to rotate, the signal coding switch formed by the brushes 4| and 42 and the commutator 5:38 is inefiective to control the magnet winding 33 of the magnet valve device I3, because in this instance it is controlled directly by the contact I) of the rela I9.

Upon the pick-up of the relay I9, therefore, the magnet winding of the magnet valve device I3 is energized and the magnet valve device I3 accordingly operated to cause air under pressure to be supplied to operate the horn I I continuously until such time as the relay I9 is restored to its dropped-out position.

The horn l I accordingly operates to produce a continuous audible signal or blast, indicative of the all clear signal, until such time as the cam disk 46 of the coding and timing device I4 completes a full revolution from the time the relay I9 was initially picked-up. At the expiration of the time required for a full revolution of the cam disk 56, the switch 48 is opened momentarily in the manner previousl described for the switch 4i, thereby interrupting the self-holding circuit for the winding of the relay I9 and causing the contacts of this relay to be restored to dropped-out position.

Upon the restoration of the contacts of the relay I9 to their dropped-out positions, the magnet winding 33 of the magnet valve device I3 is deenergized, as is the armature winding and field winding of the motor I5. Accordingly, the supply of air to the horn II is cut-oil and the audible signal produced thereby is terminated. At the same time, the motor I5 coasts to a stop promptly, in the manner previously described, so as to cause reclosure of the switch 48. Reclosure of the switch 48 renders the self-holding circuit for the winding of the relay I9 potentiall effective again subject to subsequent pick-up of the relay I9.

If the local operator desires to cause operation of the horn II to produce a continuous blast indicative of the all clear signal, he may do so by momentarily closing the push button switch 22. The push button switch 22 is connected in parallel to the contact a of the relay ii and consequently the momentary closure of the switch 22 operates in the same manner as if the relay I? were picked-up. Accordingly, it is deemed unnecessary to describe the operation of the equipment in response to the closure of the switch 22.

If for any reason the local operator desires to cut the remotelycontrolled relay Ii out of operation, he may do so merely by opening the cut-out switch 292). The cut-out switch 2% is connected in series with the contact a of the relay I"! and the winding of the relay I9 and is therefore effective in its open position to prevent the energization of the winding of the relay i9 by pick-up of the contact of the relay I'l'. At the same time, the opening of the cut-out switch 2% does not prevent pick-up of the relay I9 by operation of th push button switch 22.

Modification shown in Figure 5 Referring to .Fig. 5, a modification of the equipment shown in Fig. 1 is disclosed in which an electrically operated horn I IA is employed rather than the air operated horn i I. In such case, the reservoir I2 is unnecessary and is therefore dispensed with. The equipment of Fig. 5 is thus substantially identical with that in Fig. 1 except that the electroresponsive element in the horn HA is substituted for the magnet winding '33 of the magnet valve device I3 in the circuit including the wire 64 controlled either by the signal coding switch device I4 or contact 27 of the relay I9.

Description of system shown in Figure 6 The air raid warning system shown in Fig. 6 is similar to that in Fig. 1 in that it comprises an air operated horn I I, a source of air under pressure including the reservoir i2 and a magnet valve device Ilia similar to magnet valve device I3, for controlling the supply of air under pressure from the reservoir I2 to the horn H.

In other respects the system shown in Fig. 6 is substantially dififerent from that in Fig. 1. The apparatus for controlling the operation f the horn I I to produce a coded signal indicative of air raid or all clear comprises two coding relays 15 and 16 respectively, with which are associated two electrical condensers ii and it respectively; two control relays l9 and Bil; and two push button switches 8! and 82.

The apparatus for timing the duration of a coded signal sequence comprises a pneumatic timing switch device a magnet valve device 35 controlling the operation of the timing switch 85; and a choke device8l for controlling the rate of flow or air under-pressure from the reservoir I2 to the timing switch 85.

Relays I and 16 may be of the direct-current neutral type. Each of these relays has a winding W, a front contact a and a back contact b. The front contact of each relay is in open position when the winding of the relay is deenergized and is actuated to the picked-up or closed position when the winding of the relay is energized. The back contact I) of each relay is closed in the dropped-out position and is' actuated to the picked-up or open position in response to energization of the winding of the relay.

The control relays I9 and 89 are identical, each having two operatin windings a and b, and three front contacts 0, d, and e, respectively.

The winding a of each of the relays is connected in a suitable circuit to a remote control station, such as a telephone exchange, and is effective when energized to cause pick-up of the contacts of the relay.

The winding b of each of the relays I9 and 80 is a self-holding and pick-up winding effective when energized to either pick-up the contacts of the relay or maintain them picked-up if already actuated to the picked-up position.

When the contact 0 of each of the relays I9 and 80 is actuated to its picked-up or closed position, it establishes a self-holding circuit for the winding 1) of the corresponding relay which circuit extends from the positive bus wire 24 through the series-connected contact 0 of the relay and the corresponding winding b of the relay to the negative bus wire 25.

The push button switches 8| and 82 correspond to the push button switches 2| and 22 of Fig. 1 and are connected in parallel relation to the contact 0 of the relays I9 and 80 respectively. It will accordingly be seen that closure of the switches BI and 82 causes energization of the winding 1) of the corresponding relays I9 and 80 to cause pick-up thereof, the winding b being thereafter maintained energized due to the closure of the corresponding contact 0 notwithstanding the subsequent opening of the switch 8| or 82.

The timing switchdevice 85, as diagrammatically shown, comprises a movable contact m and two cooperating stationary insulated contacts s. The switch formed by the movable contact m and stationary contacts s controls connection of the positive bus wire 24 to the positive terminal of the battery 23. As shown, the movable contact 122 is carried in insulated relation on a stem 89 of a piston 9| that operates in the bore 92 of a suitable casing member 93. A coil spring 90 interposed between one face of the piston 9| and the closed end of the casing 93 yieldingly urges the piston 9| into seated relation on an annular rib seat 94 surrounding a port 95 that opens into a suitable chamber or volume reservoir 96.

In the seated position of the piston 9|, the movable contact 111. engages the stationary contacts s, thereby connecting the positive bus wire 24 to the positive terminal of the battery 23.

Upon the supply of air under pressure to the volume reservoir 96 at a selected rate, in the manner presently to be described, a certain length of time is required to build-up sufficient pressure on the inner seated area of the piston 9I to overcome the force of the spring 90. When the piston 9| is unseated from the annular rib seat 94, the increased area of the piston 9| subject to the air pressure in the volume reservoir 96 causes the piston to be snapped suddenly upward to a limiting position determined by engagement with a boss 91 within the casing 93, thereby causing the movable contact m to be suddenly disengaged from the stationary contacts s, that is, operated to open position.

A port 99 in the casing 93 servesto prevent dash-pot action of the piston 9| and the consequent delay in the opening of the switch.

The magnet valve device 86 controls the supply of air from the reservoir I2 to the volume reservoir 96. As shown, the magnet valve device 86 comprises two oppositely seating poppet valves IOI and I02 operated in one direction to unseated and seated positions respectively by a coil spring I03 and in the opposite direction to seated and unseated positions in response to energization of a magnet winding or solenoid I04.

The valve I0| is contained in a chamber I05 that is constantly open to atmosphere through an exhaust port I06 and its fluted stern extends through a suitable bore into a chamber I01 that is constantly connected by a pipe I08 to the volume reservoir 96.

The valve I02 is contained in a chamber I09 that is connected by a pipe H0 and a branch pipe III to the reservoir I2, the choke device 81 being interposed in the pipe IIO between the pipe I II and the chamber I09. The fluted stem of the valve I02 extends through a suitable port into the chamber I01 and engages the end of the fluted stem of the valve IOI in end-to-end relation.

It will thus be apparent that when the winding I04 of the magnet valve device 86 is deenergized, the air under pressure in volume reservoir 96 is exhausted to atmosphere through the exhaust port I06 in the magnet valve device. It will also be apparent that when the magnet winding I04 of the magnet valve device 86 is energized, the exhaust communication just described is closed, due to seating of the valve IOI, and a supply communication is opened due to the unseating of the valve I02 through which air under pressure is supplied from the reservoir I2 to the volume reservoir 96 at the controlled rate determined by the flow area of the choke device 81.

As previously indicated, the rate of supply of air under pressure to the volume reservoir 96 is so controlled by the choke device 81 that a certain length of time, such as two minutes, is required in order to build-up a sufficient pressure within the chamber 96 to cause upward unseating movement of the piston and the consequent opening of the contacts of the switch device 85.

Operation of system shown in Figure 6' Let it be assumed that the operator at the remote control station desires to cause operation of the horn II to produce a coded air raid signal, and that he accordingly causes the winding a of the relay of the control relay I9 to be energized.

The contacts of relay 19 are accordingly actuated to their respective picked-up or closed positions in whichthe contact 0 is effective to establish the self-holding circuit of the winding 1) of the relay 19 in the manner previously indicated. The contacts of relay I9 accordingly remain picked-up notwithstanding the deenergization of the winding a of the relay 19, until such time as the self-holding circuit for the winding b of the relay I9 is interrupted in the manner hereinafter to be described.

The contact d of the relay I9 is effective in its picked-up or closed position to establish a circuit for energizing the magnet winding I04 of the magnet valve device 06. This circuit extends from the positive bus wire 24 by way of a branch wire I I5, wire [I6 including in series relation therein contact at of relay I9 and the winding I 04 01 the magnet valve device 86 to a wire II! which is, in turn, connected to the negative bus wire 25.

The magnet valve device 86 is accordingly operated to cause air under pressure to be supplied at a controlled rate from the reservoir I2 to the volume reservoir 98, thereby to cause opening of the timing switch 85 at the expiration of a certain length of time, such as two minutes.

The contact 6 of the relay I9 is efiective in its picked-up or closed position to establish a circuit for energizing the winding of the relay l6 and for charging the condenser I8. Thi circuit extends from positive bus wire 24 by way of the branch wire I I5, contact 6 of relay III, a wire H8 including the back contact I) of relay I5, through the parallel-connected winding W of relay IG and the condenser I8 to a 'wire IIS that is connected to the negative bus wire 25.

The condenser I8 is accordingly charged to a voltage corresponding to the battery voltage impressed on the bus Wires 24 and 25 and the contacts of the relay I6 are, at substantially the same time actuated to their respective picked-up positions.

The contact a of the relay I is efiective in its picked-up or closed position to establish a circuit for energizing the winding W of the relay I5 and for charging the condenser 11. This circuit extends from the positive bu wire 24 by way of a branch wire I2I, a second branch wire I22 including the contact a of the relay I6, the parallel connected winding W of relay l5 and condenser I1, and a wire I23 to the negative bus Wire 25. The condenser 11 is accordingly charged to the voltage impressed on the bus wires 24 and 25 and the contacts of the relay I5 are substantially simultaneously actuated to their respective picked-up positions.

The back contact I) of relay I5 is effective in its picked-up position to open the circuit for energizing the winding W of the relay I6 and for charging the condenser I8. The contact of the relay 16 are not, however, restored at once to their dropped-out position because the condenser I8 discharges current locally through the winding W of the relay I6, thereby holding the contacts of the relay in their picked-up positions for a certain length of time, such as two or three seconds.

Upon the restoration of the contacts of the relay I6 to their dropped-out position, a circuit is established for energizing the winding 33 of the magnet valve device Ilia. This circuit extends from the positive bus wire 24 by way of the wire I2I, serially-connected contact b of relay It and contact a of relay 75, a wire I25, the magnet winding 33 of the magnet valve device I3a, and wire I I! to the negative bus Wire 25.

The magnet valve device I3a is accordingly operated to cause air under pressure to be supplied from the reservoir I2 to the horn II to cause the horn to produce an audible signal or blast during 1tlhe time that air continues to be supplied to the urn.

Contact a of relay I6 i efiective when restored to its dropped-out or open position to interrupt the circuit for energizing the winding W of the relay I5 and for charging the condenser I1, Like the relay I6, the relay I5 is not immediately restored to its dropped-out position but is main tained picked-up by the current discharged locally from the condenser Ii through the winding of the relay I5. After a certain interval of time, such as two or three seconds, the current discharged from the condenser II through the winding of the relay I5 diminishes sufilciently to cause restoration of the contacts of the relay I5 to their dropped-out position.

Restoration of the contact a of relay I5 to its dropped-out or open position interrupts the circuit for energizing the magnet winding 33 of the magnet valve device Isa. The magnet valve device I3a is accordingly operated to cut-cit the supply of air under pressure to the horn ii and the signal produced by the horn is thus termi nated.

The contact I) of relay ?5 is effective when restored to its dropped-out or closed position to reestablish the circuit for energizing the winding o1; relay I6 and for charging the condenser '58. The contacts of relay I5 are accordingly picked-up and the condenser I8 is charged. Pick-up of the relay I6 causes energization of the winding of the rela I5 and charging of the condenser il in the manner previously described. Pick-up of the contacts f the relay I5 interrupts the circuit for energizing the winding of the relay I0 and fo chargin the condenser 78. After a certain length of time, such as two or three seconds, the contacts of relay 76 are again restored to their dropped-out position in which the circuit for energizing the magnet winding 33 of the magnet valve device I isagain established in the manner previously described.

It will thus be apparent that the coding relays I5 and I6 continue to be alternately picked-up and dropped-out, in the manner previously described to cause the magnet winding of the magnet valve device I3a to be alternately energized and deenergized for approximately the same length of time, namely two or three seconds, thereby causing the horn I l to be periodically operated to produce audible signals of two or three seconds duration as long as the control relay l9 remains picked-up.

The control relay I9 remains picked-up until such time is the self-holding circuit for the winding 1) thereof is interrupted due to the opening of the timing switch 85. As previously explained, the timing switch is opened upon the expiration of a certain length of time, such as two minutes, following the initial energization of the magnet winding I04 of the magnet valve device 86 which occurs in response to the initial pick-up of the control relay I9.

Upon the restoration of the control relay 79 to its dropped-out position, operation of the coding relays I5 and I6 is terminated due to the inter ruption of the circuit including the contact e of the relay I9. Consequently, with the two coding relays I5 and I0 in their respective dropped-out positions, the circuit for energizing the magnet winding of the magnet valve device I3a i inter rupted and remains interrupted at the contact a of the relay I5.

The restoration of the contact d of the rela is to its dropped-out or open position interrupts the circuit for energizing the magnet winding I04 of the magnet valve device 85. The magnet valve device 86 is accordingly operated to the position shown in the drawings in which the supply of air under pressure from the reservoir I2 to the volume reservoir 96 is terminated and the air under pressure in the volume reservoir 93 isexhausted to atmosphere through the exhaust port I 06 oi the magnet valve device 88.

Upon the suiiicient exhaust of air under pressure from the volume reservoir 95, the spring 90 returns the piston SI downwardly into seated position on the annular rib seat 94, thereby reengaging the contacts of the timing switch 85. It will be apparent that the reclosing of the timing switch 85 is not effective to cause the relay 19 to be again picked-up because the contact c of the relay lil has been previously restored to it's dropped-out or open position.

If the local operator desires to cause operation of the horn I! to produce a coded "air raid signal, he may do so merely by momentarily closing the push button switch 8I thereby energizing the winding 1; of the relay I9 and causing the contacts of the relay to be actuated to their pickedup position, in which the contact is effective to establish the self-holding circuit for the winding 1) of the relay. Thereafter the push button switch 31 may he opened and the relay I9 remain in its picked-up position.

In view of the fact that the operation of the system is the same as previously described once the relay i8 is picked-up, it is not necessary to repeat a description of such operation.

Let it now be supposed that the operator at the remote control station desires to cause operation of the horn II to produce an all clear signal. To do so he causes the winding a of the control relay 8% to be energized and the contacts of the relay accordingly actuated to the picked-up position. The self-holding circuit for the winding b of relay 8!! is accordingly established by contact c of relay 33 in its picked-up or closed position, and thereafter the winding a of the relay 8!! may be deenergized without causing the contacts of the relay to be restored to their dropped-out position.

The contact ol of the relay 8!] is efl'ective in its picked-up or closed position to establish a circuit for energizing the magnet winding I04 of the magnet valve device 85. This circuit extends from the positive bus wire 24 by way of the branch wire I2I, contact at of the relay 80, wire H6, magnet winding I84 of magnet valve device 83, and wire l I! to the negative bus wire 25. The magnet valve device 85 is accordingly operated to cause air under pressure to be supplied at a rate controlled by choke device 81 from the reservoir I2 to the volume reservoir 85 as long as the relay 8!! remains picked-up.

The contact e of the relay 8!! is effective in its picked-up or closed position to establish a circuit for energizing the winding of the relay I and charging the condenser 11. This circuit ex ends from the positive bus wire 24 by way of the branch w re I2I. a wire I2I including the contact e of the relay so, wire I22, the parallel connected winding W of relay !5 and condenser 11, and wire I23 to the negative bus wire 25. The condenser 11 is accordingly charged and the contacts of the relay l5 are actuated to their picked-up position.

The contact a of the relay I5 is effective in its picked-up or closed position to establish the circuit for energizing the magnet winding 33 or the magnet valve device I3a, which circuit has been previously traced. The magnet valve l3a is accordingly operated to cause air under pressure to be supplied from the reservoir I2 to the horn I I to cause it to operate to produce its audible signal.

In this instance, however, the relay I6 remains in its dropped-out position and the relay 15 remains'ln its picked-up position as long as therelay remains in its picked-up position. Accordingly, the magnet valve device I3a causes air under pressure to be supplied continuously to the horn II until such time a the relay 80 is restored to its dropped-out position as a result of the interruption of the self-holding circuit of the winding b of relay 8!! due to the opening of the timing switch 85.

As in the case of an air raid signal, the timing switch is actuated to its open position at the expiration of a certain time, such as two minutes', following the initial pick-up of the relay 86. It will accordingly be seen that the horn l I continues to produce a continuou audible signal for a predetermined length of time, such as two minutes, to indicate the all clear" signal.

Upon the interruption of the self-holding circuit for the winding 1) of relay 83 due to the opening of the timing switch as, the contacts of the relay so are restored to their dropped-out position. The contact (1 of relay 88 is effective in its dropped-out or open position to interrupt the circuit f or energizing the magnet windin I at of the magnet valve device 86. Magnet valve device 86 is thus operated to cut-ofi the supply of air under pressure to the volume reservoir and to cause air under pressure to be exhausted from the volume reservoir 96 to atmosphere through the exhaust port I96. Upon suflicient reduction of the pressure in the volume reservoir 96, the timing switch 85 is restored to its closed position.

Contact 6 of the relay 8!] is effective in its dropped-out position to interrupt the circuit for energizing the winding W of the relay I5. After a certain length of time, such as two or three sec onds, during which the condenser l! discharges current through the winding of the relay I5, the contacts of the relay I5 are restored to their dropped-out position. The restoration of the contact a of the relay I5 to its dropped-out or open position interrupts the circuit for energizing the magnet winding 33 of the magnet valve device I3a. The magnet valve device I3a is thus operated to cut-ofi the supply of air under pressure from the reservoir I2 to the horn II which accordingly ceases to produce the audible signal.

If the local operator desires to cause operation of the horn II to produce the all clear signal. he may do so merely by momentarily closing the push button switch 82. Momentary closure of the switch 82 causes pick-up of the relay 8!) which is accordingly stuck-up thereafter by the self-holding circuit of the relay. Operation of the system is thereafter the same as that, previously described, initiated by an operator at a remote control station and is accordingly not repeated.

System shown in Figure 7 The air raid warning system shown in Fig. 7 is for the most part identical with that shown in Fig. 6, difiering therefrom in the omission of the two coding relays l5 and i3 and the two condensers I1 and I8 and the substitution therefor of a single coding relay 15A, an electrical condenser HA, and three adjustable resistors I3I, I32, and I33, respectively.

Those parts of the system shown in Fig. 7 which correspond identically to corresponding parts in the system shown in Fig. 6 are identified by the same reference numerals without further description.

The coding relay 15A is of the direct-current neutral type having two separate windings o Operation of system shown in Figure 7 Let it be assumed that the operator at the remote control station desires to cause operation of the horn I I to produce an air raid signal and accordingly causes the winding a of the relay 79 to be energized momentarily. Contact of the relay I9 is effective in its picked-up position to establish the self-holding circuit for the winding b of the relay 19 to maintain the relay picked-up notwithstanding subsequent deenergization of the winding (1 of the relay 19.

The contact at of the relay 779 is effective in its picked-up or closed position to establish a circuit for energizing the magnet winding Ill i of the magnet valve device 85 in exactly the same manner as in the system shown in Fig. 6. The magnet valve device 85 is accordingly operated to cause air under pressure to be supplied from the reservoir 52 to the volume reservoir as of the timing switch 85 at a controlled rate determined by the choke device 81.

Contact e of the relay is is eifective in its picked-up position to establish a circuit for energizing the winding a of the coding relay 55A and for charging the condenser MA. This circuit extends from the positive bus wire 24 by way of the branch wire H5, contact 6 of the relay i9, wire I35, back contact e of the coding relay A, resistor I3I, a wire I36 to the point I37 where the circuit divides into two parallel branches, one branch including the condenser TIA and the other branch including the resistor I32 and the winding (1 of the coding relay 15A, the two branches rejoining at the point I thence by way of a wire I3i and a wire MI to the negative bus wire 25.

The condenser TIA is accordingly charged and the contacts of the relay 55A actuated to their picked-up positions.

The back contact e of the relay 75A is effective in its picked-up or open position to interrupt the energizing circuit for the winding a of the relay 15A and the charging circuit for the condenser TIA. The contacts of the relay 75A are not immediately restored to their dropped-out position, however, because the condenser HA discharges current locally through resistor E32 and winding rt of the relay 15A as well as through the winding 73 of the relay 15A and the resistor I33.

The contact c of the coding relay 55A is effective in its picked-up position to establish the circuit including the Winding b of the relay 75A and the resistor I 33 in the manner readily apparent in the drawings.

The resistors I32 and I33 may be adjusted in value to so control the current discharged from condenser TIA to the respective windings a and b of the relay 55A as to vary the time that the contacts of the relay remain held in their picked-up position due to the current discharged from the condenser. They may be so adjusted, for example, as to cause the contacts of the relay 15A to remain in their picked-up positions for at least three seconds following the pick-up or the relay contacts.

The contact d of the relay 75A is effective in its picked-up or closed position to establish a circuit for energizing the magnet winding 33 of the magnet valve device I311. This circuit extends from the positive bus wire 24 by way of the branch wire I 2i, a wire let including the contact d of the relay 15A, magnet winding 33 of the magnet valve device I311, and the wire II! to the negative bus wire 25.

The magnet valve device I3a is accordingly operated as in the system of Fig. 6 to cause air under pressure to be supplied to the horn SI to cause an audible signal to be produced as long as the magnet winding 33 thereof is energized.

Upon the restoration of the contacts of the relay I'EA to their dropped-out position, contact e of relay 15A is effective to reestablish the circuit for energizing the winding (1 of the relay 75A and for charging the condenser HA. The resistor I3I in the circuit, functions to delay for a certain length of time such as two or three seconds the pick-up of the contacts of the relay. During this interval of time the contact 0 of the relay 15A is in open position interrupting the circuit for the magnet winding of the magnet valve device I3a. During such interval of time, the magnet valve device I3a accordingly cuts-off the supply of air under pressure to horn I I, thereby causing cessation of the audible signal.

When the contacts of the relay 15A are again picked-up, the circuit for energizing the magnet winding of the magnet valve device I3a is again established for the interval of time corresponding to the time that the contacts of the relay iEA remain held in their picked-up position by the current discharged from the condenser I'IA.

It will thus be apparent that as long as the relay I9 remains picked-up, the coding relay EEA will be alternately picked-up and dropped-out to cause the magnet valve device Ida to be operated in such a manner as to alternately supply and cut-cit the supply of air to the horn II, thereby causing'the horn to produce periodic blasts in substantially the same manner as in the system of Fig. 6.

Upon the expiration of a certain length of time, such as two minutes, the timing switch opens and accordingly interrupts the self-holding circuit for winding 12 of the relay 19, thereby causing restoration of the contacts of the relay 7%) to their dropped-out position.

The magnet winding of the magnet valve 36 accordingly deenergized and the magnet valve operated to terminate the further supply of air under presure to the timing switch and to cause an exhaust of air under pressure from the volume reservoir 96 whereby the timing switch 85 is restored to its closed position.

At the same time, the restoration of the contact 6 of the relay ?9 to its dropped-out or open position causes the coding relay 55A to cease further operation and remain in its dropped-out position wherein the circuit for energizing the magnet Winding of the magnet valve device I3a is interrupted.

t will accordingly be seen that the system operates automatically in response to the pickup of the relay 79 to cause operation of the horn Ii to produce periodic audible signals for a certain length of time, such as two minutes.

An air raid signal may also be initiated by a local operator momentarily closing the pick-up switch 8| just as in the system of Fig. i.

If the operator at a remote control station desires to cause operation of the horn i I to produce the all clear signal, he may initiate such operation by causing momentary ener ization of the winding is of the relay 88. Once the contacts of the relay at are actuated to their picked=up position the self-holding circuit for the winding b of the relay is established by the contact 0 thereof as in the system of Fig. 6.

The contact :1 of the relay 8!! is effective in its picked-up or closed position to establish the circuit for energizing the magnet winding 184 of the magnet valve device '86. The magnet valve device 86 is accordingly operated to cause air under pressure to be supplied from the reservoir l2 to the volume chamber .95 of the timing switch 85 at a controlied rate determined by the choke device 8?.

Contact e of the relay 8!] is effective in its picked-up or closed position to establish a circuit for energizing the winding 0, of the coding relay A as well as for charging the condenser 115.

This circuit extends from the positive bus wire 24 by way of the Wire i2l, a branch wire l4! including the contact e of the relay 80 to the wire I at the point 37, thence through the two parallel branches including respectively the condenser HA and resistor I32 and winding a of relay 75A to the point 13-8, and thence by wires 139 and NH to the negative bus wire 25.

The coding relay 75A is accordingly picked-up and maintained picked-up as lon as the relay 3 remains picked-up.

fhe magnet winding of the magnet valve device 13a is accordingly continuously energized as long as the relay 15A is picked-up to cause air under pressure to be supplied to the horn H by the magnet valve device 13a.

Vfnen the timing switch 85 is opened at the expiration of a certain time, such as two minutes. following the initial pick-up of the relay 89 to effect the interruption of the self-holding circuit O}. the relay and the consequent restoration. of the contacts of the relay to their dropped-out position, the circuits for energizing the magnet windings of the magnet valve devices 88 and I321 are accordingly interrupted and further operation of the horn terminated just as in the system of Fig. 6.

The contacts of the relay 15A will be maintained picked-up for a certain short interval of time, such as occurs during an air raid signal due to the discharge of the current from the condenser HA through the windings a and b of the relay following the restoration of the contact e of the relay 80 to its dropped-out or open posi tion. Actually, therefore, the horn H continues to produce an audible signal for a short interval of time of the order of several seconds following the drop-out of the relay 80.

The local operator may initiate an all clear signal operation of the horn I l merely by momentarily closing the push button switch 82, just as in the system of Fig. 6.

Summary Summarizing, it will be seen that I have disclosed several embodiments of an air raid warning system, all of which are automatically operative to cause any selected one of a plurality of coded signals to be produced by an audible signal device, such as an air operated horn. All of the systems described, moreover, are effective to cause the signal device to operate to produce a selected coded signal for a certain length of time, such as two minutes, in response to a momentary control impulse or o eration.

In one embodiment, a combination coding and timing apparatus driven by an electric motor is provided.

In the other embodiments. a pneumatic timing switch mechanism is provided which is set in operation in response to the initiating momentary control impulse for timing the duration of the signal sequence. In one of the latter two emvbodiments, two cooperating coding relays are provided eifective to cause intermittent operation of the horn. One of these relays is effective upon operation to produce a continuous operation of the horn.

In the other of the last two mentioned embodiments, at single coding relay is provided, which is alternately picked-up and dropped-out, at one time, to cause intermittent operation of the horn and whichis-continuously picked-up to cause continuous operation of the horn, at another time, dependent upon the particular signal selected.

Having now described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. In a signal system having a signal device, the combination of two electrical relays, each of said relays having two separate windings, one of which is effective when energized to cause pickup of the relay and the other of which is effective when energized to maintain said relay picked-up, means responsive to the pick-up of each of said relays for establishing a self-holding circuit in cluding the said other winding of the corresponding relay whereby to maintain the corresponding relay picked-up, means set in operation in response to the pick-up of one of said relays for causing operation of said signal device to produce one certain signal so long as said relay is pickedup, means set in operation in response to the pickup of the other of said relays to cause operation of said signal device to produce a different signal so long as said other rela is picked-up, and timing means set in operation in response to the pickup of either of said relays for interrupting the self-holding circuit for either of said relays and effecting the consequent restoration of the relays to their dropped-out position at the expiration of a certain length of time.

2. .In a signal system having a signal device, the combination of two electrical relays each having a winding effective upon energization to cause pick-up of the relay, means eifective in response to pick-up of each of said relays for causing continued energization of the winding of the corresponding relay whereby to maintain the relay picked-up, means automatically operative as long as one of said relays is picked-up for causing operation of said signal device to produce one certain signal, means operative so long as the other of said relays is picked-up to cause operation of said signal device to produce a certain diiferent signal, and pneumatic timing means set in operation in response to pick-up of either of said relays for eifecting deenergization of the winding of the corresponding relay and the consequent restoration thereof to its dropped-out position at the expiration of a certain length of time following the initial pick-up of the relay.

3. In a signal system having a signal device, the combination of a control relay having a winding effective when energized to cause pick-up of the relay, means effective in response to pick-up of said control relay for causing continued energization of the winding of said control relay to maintain it picked-up, a coding relay, means effective as long as said control relay is picked-up for causing said coding relay to be alternately pickedup and dropped-out at predetermined intervals, means controlled by said coding relay for causing said signal device to be operated periodically, and timing means set in operation in response to the pick-up of said control relay for effecting deenergization of the winding of said control relay and the consequent restoration of the relay to its dropped-out position at the expiration of a certain length of time following the pick-up of the control relay, whereby to terminate the alternate pick-up and drop-out of said coding relay and the consequent periodic operation of said signal device.

4. In a signal system having a signal device, the combination of two selectively operable control devices, a coding relay, means responsive to operation of one of said control devices for causing said coding relay to be alternately picked-up and dropped-out repeatedly for predetermined lengths of time respectively, means responsive to the operation of the other of said control devices for causing said coding relay to be continuously picked-up, means controlled by said coding relay and efiective to cause operation of said signal device only while said relay is picked-up, and means for restoring said coding relay to its dropped-out position following the operation of either of said control devices so as to terminate the operation of said signal device.

5. In a signal system having a signal device, the combination of two selectivel operable control devices, a coding relay, means responsive to operation of one of said control devices for causing said coding relay to be alternately picked-up and dropped-out repeatedly for predetermined lengths of time respectively, means responsive to the operation of the other of said control devices for causing said coding relay to be continuously picked-up, means controlled by said coding relay and effective to cause operation of said signal device only While said relay is picked-up, and

timing means set in operation in response to the operation of either of said control devices and efiective at the expiration of a certain length of time following the operation of either of the said control devices for restoring said coding relay to its dropped-out position so as to terminate the operation of said signal device.

6. In a signal system having a signal device. the combination of two relays each of which has a winding selectively energizable under the control of an operator for effecting pick-up of the relay, means effective in response to the pickup of each of said relays to cause continued energization of the winding of the relay whereby to maintain the relay picked-up, a coding relay, means effective while one of said relays is Pickedup for causing said coding relay to be alternately picked-up and dropped-out repeatedly for predetermined lengths of time respectively, means efiective while the other of said two relays is picked-up for causing said coding relay to be continuously picked-up, means controlled by said coding relay and effective in response to the alternate pick-up and drop-out of the coding relay to cause periodic operation of said signal device and also operative in response to the continued pick-up of said coding relay for causing continuous operation of said signal device, and timing means set in operation in response to the pick-up of either of said two relays effective to cause deenergization of the winding of the picked-up relay at the expiration of a certain length of time whereby to cause restoration of said coding relay to its dropped-out position and the consequent termination of the operation of said si nal device.

7. In a signal system, the combination of an air operated signal device effective to produce an audible signal upon the supply of air under pressure thereto, a source of air under pressure, electroresponsive valve means operative only while energized to cause air under pressure to be supplied from said source to said air operated signal device, a volume reservoir, an electroresponsive valve device effective while deenergized to vent said volume reservoir to atmosphere and operative only while energized to cause air under pressure to be supplied at a controlled rate from said source to said volume reservoir to cause an air pressure exceeding a certain value to be builtup therein only after the elapse of a certain length of time following initiation of the supply of air to said volume reservoir, means operative to effect periodic energization of said electroresponsive valve means and the consequent supply of air under pressure by said electroresponsive valve means to said air operated signal de vice periodically to thereby cause said signal device to produce a predetermined signal, means efi'ective while the last said means is operative for causing continued energization of said electroresponsive valve device and the consequent continued supply of air under pressure by said electroresponsive valve device to said volume reservoir, and a pressure operated switch device responsive to an air pressure in said volume reservoir exceeding said certain value for causing deenergization of said electroresponsive valve means and deenergization of said electroresponsive valve device.

CLAUDE M. HINES. 

